The angle grinder, the abrasives mounted on it, and the user have an almost symbiotic relationship: Each affects the other. They all depend upon one another to get the job done and achieve successful results.

The relationship may ultimately determine whether or not the time has come to replace that angle grinder of yours. It may determine how quickly you go through wheels and discs. It may determine your overall safety, well-being, and performance.

It’s a topic that’s more layered than you might think—one that can have an impact on safety, productivity, and consumables costs—all of which affect the bottom line.

“The biggest suggestion would be if you're making an investment in improving the productivity in your shop, look at the whole picture, all those factors that might affect performance,” said Matthew King, lead application engineer at 3M.

Angle Grinder Life and Red Flags

Sooner or later, that favorite angle grinder will need to be repaired or replaced altogether. If used exclusively for DIY or small home fabrication projects, a grinder may last a while. But it might be a different story if that tool is used to grind down welds in a high-production environment.

If the right grinder for the application is chosen and used correctly, the tool should last around a year before needing service, explained Stuart Sellers, senior sales and marketing manager for DEWALT. After three years, a user might consider replacing a grinding tool with another if repair costs begin to outweigh the price tag of a new one.

Nikki Brandt, senior product manager for DEWALT, said grinders begin to fail for various reasons, including:

• Improper care, such as air intake screens not being cleaned regularly
• Using a tool that is too small for the application
• Incorrect abrasives selection
• Improper voltage

“Failures that make a grinder stop immediately such as a bad switch or cut cord are more obvious red flags, but reduction in power is a good indication that the grinder needs to be serviced or replaced,” he said.

Brandt, meanwhile, said users also should be on the lookout for inconsistent angle grinder performance not due to accessories or power supply; an increase in vibration that makes the power tool uncomfortable and uncontrollable; and an excessively hot tool when in use, even with proper ventilation and breaks.

The User’s Role in Angle Grinder Performance

The user plays a role in an angle grinder’s longevity just as much as the tool and consumable. Applying too much pressure to the angle grinder may negatively affect it.

“Pushing too hard is going to create more stress on that grinder,” said Tony Hufford, metal fabrication category manager for Weiler Abrasives. “If you’re not using the right abrasive and try to correct that by pushing harder, you’re just going to create extra stress and possibly create a safety concern.”

The extra stress that results when applying too much pressure during a grinding process will not only impact the grinder’s life but also the life of the abrasive. Jeremy Spencer, product manager for Norton | Saint-Gobain Abrasives, said shops that are burning through well-made angle grinders may not be getting the full life of their wheels and discs.

Say the consumable meant to last 15 minutes is only reaching five minutes of life. Spencer said it’s a sign that the user is applying too much pressure while grinding. As a result, the shop is getting less in return from its discs and wheels while generating unnecessary strain on the grinder.

“For your company’s bottom line, abrasives are not inexpensive, no matter where you buy them from,” Spencer said. “They add to overall job cost because they're a consumable. When applying too much pressure, you're costing yourself grinders and you're costing yourself abrasives.”

Using an angle grinder and its consumables properly is critical for their longevity, Hufford added.

“If you use a cutting wheel, use it with a slight motion back and forth. If you’re not pressing too hard on that cutting wheel and you get the feel just right, you can significantly increase the life while maintaining cutting speed,” Hufford said. “And depending on the material you’re cutting and the application, you need to make sure you're choosing the right abrasive type, right formulation, and right thickness of the cutting wheel as it will allow you to be more efficient and reduce chances of cross contamination.”

Safety should be a top priority. A safer tool and a safer work environment will make everyone happier in the long run. According to Spencer, a deteriorating grinder could lead to injury and other unwanted issues.

“Management should safely consider grinder usage as a key practice because it impacts operators and overall process productivity. Safe practices affect the consumables being used; it can affect workpiece quality,” he added.

Angle Grinder Types

Angle grinders are available in both cordless or corded models and are powered by an electric motor or a pneumatic system.

Historically, Sellers explained, cordless grinders are best suited for intermittent use, while corded models work best for continuous use. With the advancements made in cordless technology, a cordless grinder now can offer the same performance as a corded model without the hassles and safety hazards of a cord.

Electric- or pneumatic-powered angle grinders both have their respective pros and cons.

“With a pneumatic grinder, sometimes it's as simple as changing and replacing the veins inside,” said 3M’s King regarding pneumatic tool maintenance. “A simple teardown, putting a new part in, putting it back together, and off you go.

“With electric grinders, you may see customers buy a more affordable tool. When it fails or needs replacement, they may either send that tool back to the manufacturer for a partial credit [or] scrap the tool and buy a new one.”

King added that a grinder with an electric motor may be more reliable—users know what to expect when they plug it into a power source. Pneumatic grinder performance, however, depends on multiple variables.

“With pneumatic, the amount of power you're going to get will be dependent on the type of hose that you're using, the diameter of the hose, the air supply itself, how many other people are using that same air supply,” King said.

“You may have 100 PSI ... if one person's running, you get 100 PSI. If 30 people are running, you might be down to the high 70s, low 80s, and maybe not getting the amount of air that is required to allow it to perform at its optimum level or its design level,” he added.

The Importance of Matching the Angle Grinder to the Application

The saying ‘You get what you pay for’ applies almost perfectly when it comes to angle grinders, said King. The higher-priced models tend to perform better, last longer, and are less susceptible to breaking down.

“If one of the most critical parts of their operation—which is the grinder itself—is not optimum for the performance of the abrasives that they're buying, they may not get the life out of the abrasive, they may not get the use out of the abrasive they want, so their investment might be shot on both ends,” he said.

“The advice that I always give customers is that while you're investing in the proper abrasive to do the job and cut down on the amount of labor it takes to achieve your desired result—whether it's a bevel or a weld removal or cleaning a surface—you have to pay an equal amount of attention to the tool that's going to be running that abrasive,” King added.

A lower-cost grinder likely generates less amperage, Spencer said. Users should consider this when making a grinder purchase. A lower-cost model may save a shop money at first, but it might require a quicker replacement because its amperage limitations can’t handle the work.

“Grinders with heavy-duty electric motors are likely not available at a really low price," Spencer explained. "A low-cost grinder with less amperage is probably not going to last long if you are grinding huge welds all day.”

Keep in mind the different sizes. Spencer said sometimes a 4.5-in. grinder is all you need postweld if you’re welding framework.

But what happens if you decide to use that smaller grinder for the fabrication of tanks? While heavier, a 7- or 9-in. grinder will better suit such work, thus reducing the risk of overloading the tool.

“If you're going to be building tanks, oil-filled tanks or similar things, you're going to be beveling ½-in. steel and have welds that are the length of these tanks, then maybe you’re asking too much of a 4.5-in. grinder,” Spencer said.

Advancements in angle grinder technology have improved the performance and longevity of these power tools. For instance, Sellers said that brushless grinders have removed the No. 1 wear item—the brushes—from the equation. Thermal overload protection, meanwhile, shuts grinders down before they become overheated.

Many angle grinders now are equipped with exhaust systems to dissipate heat, enhancing the tool's performance and longevity, added Brandt. Airflow design advancements should further optimize the two.

Among other improvements, Brandt said battery innovations have introduced more efficient power management systems to extend tool run-times and lifespans. And soft start technology gradually increases the speed of the motor at startup, reducing stress on the motor.

The Role of the Abrasive

What about the abrasive product attached to the angle grinder—does it play a role in an angle grinder’s lifespan? According to Spencer, it can.

“An abrasive disc that's new is going to be able to grind more aggressively than one that's worn out. However, sometimes when a disc is worn out, operators push it just a little harder and longer if they’re almost done with a job,” he added. “But most grinder operators know to switch out the disc because they get tired of pushing.”

Advancements in abrasive grains, like shaped grains, also have changed how much pressure is required by the user.

“Let the grinder, the weight of the grinder, and the disc do its job. You're not having to push continuously like you would on some of the conventional abrasives. For example, using an engineered grain abrasive disc will likely enable a 5- or 4.5-in. grinder to be used versus a heavier 7-in. grinder,” Spencer explained.

Hufford cautioned users to be conscious when choosing high-performance abrasive products, such as those that contain ceramic alumina grains. Their performance may depend on the tool being used.

“If a grinder doesn’t have enough power, you’re not going to get the full advantage of a ceramic grain or higher-performance grain,” said Hufford. “Make sure the power of your grinder is well equipped for the grain that you’re using.”

In the end, Hufford said it’s all about what works best for what you're trying to accomplish.

“Make sure it’s performing to your expectations for your application and that you’re not just buying a wheel because of what you see from a marketing standpoint—it may or may not be best for your application.”